1. Field of the Invention
The present invention relates to a vacuum processing apparatus and a vacuum processing method. Particularly the present invention relates to a vacuum processing apparatus and a vacuum processing method capable of forming on a substrate a deposited film, specifically a functional deposited film, more specifically a deposited film of an amorphous semiconductor for use in a semiconductor device, an electrophotographic light-receiving member, an image input line sensor, an image pickup device or a photovoltaic device, by plasma CVD, further to a vacuum processing apparatus and a vacuum processing method capable of forming an amorphous silicon based electrophotographic photosensitive member by forming an amorphous silicon-based deposited film on a cylindrical substrate.
2. Related Background Art
In recent manufacture of semiconductor devices, there is frequently utilized so-called RF plasma CVD, which generally employs a high frequency of 13.56 MHz in consideration of the restriction by the radio law. Also there is proposed so-called microwave CVD utilizing microwave of a frequency of 2.45 GHz. The microwave CVD has advantages that are not achievable with the RF plasma CVD. More specifically, the microwave CVD can achieve a very large film deposition rate with an extremely high gas utilization efficiency. The microwave CVD utilizing microwave of 2.45 GHz is disclosed in Japanese Patent Application Laid-Open No. 60-186849.
In addition to such development in the method of decomposing a raw material gas, there has been developed a deposited film-forming apparatus for the purpose of stably supplying devices of high quality.
Particularly in the plasma CVD apparatus, during the formation of a deposited film on a substrate, the deposited film is also formed at the inside of the film forming apparatus, and such deposited film may be peeled off and scattered to significantly degrade the quality of the deposited film formed on the substrate. For this reason, there have been made various proposals for preventing such film peeling. For example, Japanese Patent Application Laid-Open No. 9-219373 (hereinafter referred to as "Reference 1") discloses an example of preventing the film peeling by varying the surface roughness (ten-point mean roughness Rz) of the high frequency power-introducing means from 5 .mu.m to 200 .mu.m.
Also in recent years, there is a strong demand for higher quality also for the amorphous silicon devices, because of the general improvement in the performance of the equipment utilizing the above amorphous silicon devices.
Particularly in the field of electrophotography, the aforementioned peeling of the deposited film formed inside the film forming apparatus causes collision of the peeled film to the surface of the electrophotographic substrate, thereby inducing abnormal growth, so-called "spherical projection" on the photosensitive member. Such spherical projection, after repeating image formation over a long period, may cause so-called white spots or black spots on a copied image.
In the field of electrophotography, therefore, there is required careful countermeasure against the film peeling, not only because the spherical projections directly result in an image defect to degrade an image quality, but also because a deposited film of a larger thickness and a larger area in comparison with that in other devices. Furthermore, the spherical projections of a conventionally acceptable level have now become a problem, since the recently strong demand for cost reduction and space saving for improving the office environment is accelerating the reduction of the diameter of the photosensitive member and the increase in the process speed.
For example, the spherical projections of a diameter smaller than 10 .mu.m have scarcely induced problems but have recently been found out as the cause of image defect in the case of repeating the image formation for a long period under certain conditions.
It has also been found that the control of the average roughness Rz of a portion in contact with a glow discharge provides a slightly increased effect but scarcely provides a sufficient effect on such small spherical projections.
Because of the above-described facts, there is being requested a stronger measure for preventing the film peeling than the conventional one at the portion of the deposited film-forming apparatus being in contact with the glow discharge.